摘要
在新疆西南天山科桑溶洞地区,新厘定出一套斜长角闪岩-花岗岩地质单元:侵入斜长角闪岩中的新元古代白云母花岗岩(片麻状构造)、以及侵入上述古老岩石单元的早奥陶世花岗岩(块状构造)。片麻状白云母花岗岩中锆石具有热液锆石边、岩浆锆石幔和碎屑锆石核(边-幔-核结构),剔除被热液锆石和碎屑锆石混染的SHRIMP测点,获得岩浆锆石幔的加权平均年龄752.3±5.1Ma(MSWD=0.95),代表岩浆的结晶年龄。块状花岗岩的锆石具有边-核结构,热液锆石边的U-Pb年龄(419.5±5.7Ma)明显偏低。剔除热液锆石和碎屑锆石,获得岩浆锆石的平均U-Pb年龄481.1±4.4Ma(MSWD=0.88),代表花岗岩的结晶年龄。早奥陶世早期,岩浆侵入新元古代片麻状白云母花岗岩中。在晚志留世或者更晚时期,两类花岗岩共同经受了变质热液改造,变质流体交代岩浆锆石,导致锆石溶蚀再生长。
Neoproterozoic and Early Ordovician granite intruded into amphibolite has been identified in the Kesang Rongdong region, southwestern Tianshan Mts. Zircons in the gneissic muscovite granite have hydrothermal rims, which replaced their igneous mantles with detrital cores. SHRIMP analysis on these igneous zircon mantles （without mixture of hydrothermal rim and detrital core） gives an average U-Pb age of 752. 3±5. 1Ma（ MSWD = 0. 95 ）. This age represents the magma intrusion episode. Hydrothermal zircon rim formed in the Early Ordovician granite in some cases though most zircons do not show continuous hydrothermal rim. One euhedral zircon crystal consists of detrital core and hydrothermal rim, the latter has much younger U-Pb age of 419. 5 ± 5.7Ma comparing with most other measurements. In many other cases, however, zircon is composed with igneous rim and detrital core. The average U-Pb age, corresponding to igneous zircon rims （481.1 ± 4.4Ma, MSWD = 0. 88）, represents a magma intrusion episode in the Kesang Rongdong region. Thus, the gneissic muscovite granite and amphibolite have been intruded by the Early Ordovician granite. Afterwards, these different granites have undergone metamorphism as recorded by the hydrothermal zircon, which replaced igneous
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第7期2113-2120,共8页
Acta Petrologica Sinica
基金
国家自然科学基金项目(41072041
41121062)
国家国际科技合作项目(2010DFB23390)联合资助
关键词
新元古代
早奥陶世
花岗岩
热液锆石
科桑溶洞
新疆西天山
Neoproterzoic
Early Ordovician
Granite
Hydrothermal zircon
Kesang Rongdong
Western Tianshan Mts. , Xinjiang
